ARROW Waveguide Layer Thickness Calculator
Anti-Resonant Reflective Optical Waveguides (ARROWs) are small tubes that allow for the guiding of light in air/liquid.
Here is an SEM of an ARROW constructed at BYU:
The core of this sample is 10 microns wide and 5 microns high. We construct ARROWs by depositing alternating layers of silicon dioxide and silicon nitride on a silicon substrate, defining cores, and then covering them with several more alternating layers. These layers form a Fabry-Perot cavity in the vertical (transverse) direction, trapping the light inside the tube, and allowing single-mode propagation along the length of the ARROW. Loss decreases with additional layers, so we usually use six layers below the core and six on top. To create the Fabry-Perot cavity and to minimize loss, the thicknesses and indices of the core and surrounding layers must be tightly controlled. This calculator takes the wavelength of light to be confined in the ARROW, the index of refraction of the core (usually water or air), the thickness of the core, and the index of refraction of the desired layer and calculates the optimal thickness of the layer.
The equation used to calculate ARROW layer thicknesses.